The present invention relates to a bicycle wheel, in particular a front wheel for a racing bicycle. More precisely, the invention relates to a wheel of the type comprising a rim, a hub, and a plurality of spokes having their outer ends fixed to the rim and their inner ends fixed to the hub. With reference to the position of assembly on a bike, the hub presents a right-hand anchoring portion and a left-hand anchoring portion for anchorage, respectively, of a set of right-hand spokes and a set of left-hand spokes.
The consolidated technique for mounting wheels envisages attachment of the spokes on the rim at equal distances apart in the circumferential direction. Alternately set along the circumference of the rim are the attachments for the left-hand spokes and the attachments for the right-hand spokes, i.e., with one left-hand spoke alternating with one right-hand spoke.
Albeit consolidated, this arrangement presents certain drawbacks. In particular, the rim undergoes an undulated deformation in the direction parallel to the axis of the hub because the axial component of the pull of the spokes tends to force the rim out of the optimal condition of planarity.
Usually, the stiffness of the rim is able to make up for this deformation, limiting the said deformation below a threshold where the cyclist is unable to perceive it. However, to limit the axial deformations of the rim it may be necessary to resort to an oversizing of the latter.
Other known solutions use an arrangement where the right-hand spokes and the left-hand spokes are set close to one another in twos, so as to make the points of anchorage on the rim of each right-hand spoke and of the corresponding left-hand spoke as close as possible to one another. The aim is to cause the axial component of the pull of the spokes to be offset locally, neutralizing the effect of destabilization of the rim. This known solution is, however, subject to limitations of a technological nature, such as the encumbrance of the means of attachment of the spokes (nipples or nuts), the need for space to insert the wrenches or other tools used for assembly, etc., and moreover entails limits of structural strength of the rim due to the vicinity of two holes on the wall that are subjected to the pull of the spokes. It follows that this known solution is again affected by problems of local flexure, which tend to bring the rim out of conditions of planarity.
The purpose of the present invention is to eliminate the problems regarding axial unbalancing of the forces acting on the rim which are due to the pull of the spokes.
According to the present invention, the above purpose is achieved by a wheel having the characteristics that form the subject of claim 1.
The solution according to the present invention groups the spokes together in an even number of sets of three spokes set at equal distances apart, which comprise, alternately, two right-hand spokes and one left-hand spoke, and two left-hand spokes and one right-hand spoke. In each set of three spokes, the spoke which is set singly on a given side of the wheel will be tensioned with a pull nominally twice the pull with which the two spokes of the same set acting on the opposite side of the wheel are tensioned.